Dr. Jean Dodds on recent Vaccination Legislation

By W. Jean Dodds, DVM

The following is Dr. Dodds' August 2, 2004 letter in response to the vaccination issues in the State of Maine, reprinted here with her kind permission.

W. Jean Dodds, DVM
938 Stanford Street
Santa Monica, CA 90403
310-828-4804; Fax 310-828-8251

August 2, 2004

Senator Christopher Hall
The Maine Senate
3 State House Station
Augusta, ME 04333-0003

Re:  Proposed Legislation on Vaccine Disclosure

Dear  Senator Hall:

I am writing  in support of your proposed State of Maine legislation on vaccine disclosure. I do so  as a veterinary  research/ clinician scientist, who has been actively involved in vaccination issues for 40 years.

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While vaccines have significantly reduced the incidence of serious infectious diseases over the years, increasing evidence implicates vaccines in triggering immune-mediated and other chronic disorders.  The duration of immunity from vaccination is now accepted to be at least 5 or more years for the clinically important diseases of dogs and cats. Accordingly, new vaccine protocols are recommended: 1) giving the puppy or kitten vaccine series followed by a booster at one year of age; 2) administering further boosters in a combination vaccine every three years or as split components alternating every other year until; 3) the pet reaches geriatric age, when booster vaccination is often unnecessary and may be inadvisable.  In the years between or instead of boosters, serum vaccine antibody titers can be measured to determine the adequacy of immune memory.

Vaccine antibody titer testing measures antibodies to certain diseases to determine whether an animal's immune system has responded to previous vaccinations.   This blood test helps determine whether or not an animal will be protected from the infectious disease if he/she were to be exposed.  Titers do not distinguish between immunity generated by vaccination and/or exposure to the disease, although the magnitude of immunity produced just by vaccination is usually lower. Reliable serologic vaccine titering is available from several university and commercial laboratories and the cost is reasonable.  If a given animal's humoral immune response has fallen below levels of adequate immune memory,[COMMENT1]  an appropriate vaccine booster can be administered.

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Duration of immunity (DOI) from challenge studies

Challenge studies in the cat from Cornell University  following just two doses of trivalent killed vaccine given at 8 and 12 weeks of age, showed complete protection from feline panleukopenia virus for more than 8 years, and good  protection against feline calicivirus and herpes virus for 4 and 3 years, respectively. Colorado State University recently reported long term vaccinal immunity in a large number of pet and laboratory cats.

The 2003 report of the AAHA Canine Vaccine Task Force  indicated that the DOI following challenge studies in dogs was equal to or greater than 7 years for the three canine "core" vaccines against distemper virus (CDV), parvovirus (CPV-2) and adenovirus (hepatitis, CAV-1).

Challenge of immunity studies have shown that the minimum DOI of modified live virus (MLV) CDV vaccines are 7 and 5 years for the Rockborn and Onderstepoort strains of CDV, respectively. Challenge of immunity studies for CPV-2 vaccines have shown the minimum DOI with MLV CPV-2 vaccines to be 7 years.  Challenge of immunity studies for CAV-1 have shown the minimum DOI with modified live CAV-2 vaccines to be 7 years. Based on serologic data for sterilizing immunity, the minimum DOI for CDV is 12-15 and 9 years, respectively, for the Rockborn and Onderstepoort strains of CDV; up to 10 years for CPV-2; and at least 9 years for CAV-1.

In 2002, the AVMA Council on Biologic and Therapeutic Agents (COBTA) published a landmark report on cat and dog vaccines. Some key features of that report were: "vaccination is a potent medical procedure associated with benefits and risks for animals; considerations of exposure probability, susceptibility, severity of the disease, efficacy and safety of the vaccine, potential public health concerns, and owners preferences are appropriate; individual animals will require different vaccines and vaccination programs; revaccination recommendations should be designed to create and maintain clinically relevant immunity, while minimizing adverse event potential; the practice of revaccinating animals annually is largely based on historic precedent supported by minimal scientific data; unnecessary stimulation of the immune system does not result in enhanced disease resistance and may expose animals to unnecessary risks; veterinarians should consider creating a core vaccination program for most of the animals in their practice area; core vaccines are defined as vaccines appropriate to provide protection in most animals against diseases that pose a risk of severe disease because the pathogens are virulent, highly infectious, and widely distributed in the region; current adverse event reporting systems need substantial improvement in the capture, analysis, and dissemination of information; practitioner commitment to reporting adverse events and practitioner access to timely analyses of adverse event data are essential to providing optimal animal care."

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In 2004, the following statement was endorsed by all 23 members of the ACVIM Infectious Disease Study Group and approved by the ACVIM Board:  "The American College of Veterinary Internal Medicine believes that all dogs should have a routine health examination by a veterinarian at least yearly.  At that time, vaccination needs should be determined and only those antigens deemed necessary should be administered.  We currently endorse the use of the AAHA [American Animal Hospital Association] 2003 Canine Vaccine Guidelines as an aid in determining the vaccination needs of individual dogs."

Finally, because of the potential legal liability for all medical procedures including vaccination, veterinarians need to obtain informed consent from their clients.  This means that clients need to be given information about the benefits and risks of vaccination in order to permit them to make an appropriate decision about the individual vaccine to be selected and the vaccination programs of choice.  Thus, obtaining informed consent and the client's signature on a consent form or patient chart is an important aspect of following the legal standards of duty to inform "what any reasonable, prudent person would want to know about the subject". 

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  23. Twark L, Dodds WJ. Clinical application of serum parvovirus and distemper virus antibody titers for determining revaccination strategies in healthy dogs. J Am Vet Med Assoc 217:1021-1024, 2000.

W. Jean Dodds, DVM, Hemopet, 938 Stanford Street, Santa Monica, CA 90403. Dr. Dodds is an internationally recognized authority on blood diseases in animals. She established Hemopet, the first nonprofit blood bank for animals, in the mid-1980s. Through southern California-based Hemopet, Dr. Dodds (a grantee of the National Heart, Lung, and Blood Institute, and author of over 150 research publications) provides canine blood components and blood-bank supplies throughout North America, consults in clinical pathology, and lectures worldwide.

Reproduced with permission.